Pull-through security seals in which a band or strip having locking means is pushed through a receiving opening arranged at one end of the band or strip, and is prevented from being pulled out by means of restraining means mounted in the receiving opening, are known, for example, from WO 95/27968. This reference shows among others a seal which has a flat base body with a push-through opening directed perpendicularly with respect to the surface. A looping member in the form of a flat tongue or flange is constructed directly on the base body leading away perpendicularly with respect to the push-through direction. The end of this tongue can now be guided in one direction into the push-through opening and can be pushed therethrough. A loop is formed thereby, the size of which, namely its diameter, can be influenced by the extent of the length of the tongue pushed therethrough. This loop becomes smaller with an increasing length of the tongue pushed therethrough. Since the restraining means in the push-through opening prevent a pulling back of the tongue, the loop can be opened only by breaking or tearing of the tongue.
Furthermore, pull-through security seals are also known in which the tongue is formed out of one side with an essentially circular cross section, which seals have at regular intervals ball-shaped or conically-shaped nubs which can engage resilient restraining means arranged in the push-through opening of the seal. With this it is possible to achieve a reliable locking of the tongue in one direction, and the loop can be reduced, particularly tightened, corresponding with the distances between the nubs at discrete distances corresponding with the needs.
The problem of such security seals lies in preventing a manipulation of the locking function, namely in preventing a not noticeable manipulation of the lock of closed seals to effect an opening and a subsequently closing from occurring.
Thus common security seals with flat tongues have the disadvantage that with thin small plates, after locking of the seal from the push-in side, the restraining means can be blocked. Thus it becomes possible to pull the tongues without noticeable damage out of the push-through opening and to thus open the loop. The seal can subsequently, as intended, be locked and a manipulation cannot be noticed.
The same problem occurs also in the case of pull-through seals, the tongues of which have a circular cross section and have tooth elements also having a circular cross section. In addition, such seals have the problem that with simple means, as, for example, a thin-walled sleeve in the correct dimensions, which sleeve can be manufactured with very simple means, it is possible to block, particularly to render functionless, the locking mechanism from the outlet side of the push-through opening. Thus it is possible to pull the tongue also, as already described above, again out of the push-through opening, and to open the loop, and to lock same thereafter again without such action being noticed.
The mentioned tools for both known types of seals can, due to their simple geometric design, be manufactured with simple means without great expense.
The purpose of the present invention was now to find a pull-through security seal of the mentioned type which has a high manipulation safety during locking.